Curious who uses iMac over a MBP with an external monitor? Is it mainly for front desk, businesses, and perhaps people with large homes and need stationary mac?
My last two home computers have been 27" iMacs. Each one has lasted me about 8 years and I've been happy with both of them. Nice big display, good specs, not a lot of clutter. Really good bang for the buck.
At home, I use them for making music (Ableton Live), video production (DaVinci Resolve), photo processing (Photoshop and Lightroom), and programming (various IDEs and editors). I much prefer one good display over a pair of them.
Long-term, maybe it would be more cost effective to get a Mac Mini so that I don't end up paying to replace the display when I replace the machine. But display technology seems to advance about as fast as other hardware specs do, so I suspect I'd want a new monitor at about that rate anyway.
Going forward, though, I probably won't buy another iMac. That's largely because now that I make music with Ableton Live, I want a laptop that I can (aspirationally!) take to shows to play live on.
But for well over a decade, I've been a happy iMac user. I don't care about upgradeability. I buy a machine that has the specs I want when I buy it.
An M4 iMac with 10 CPU cores, 10 GPU cores, 16GB RAM and 1TB SSD costs $1700.
A 14" MBP with 8 CPU cores, 10 GPU cores, 16GB RAM and 1TB SSD costs $2000. Before you add a 27" monitor and desktop keyboard/pointing device.
Why pay that premium if you don't actually need to carry your desktop PC around?